Buck-boost xmfr questions

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

 

[Phil Hobbs]

On 10/30/2012 01:55 PM, etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You're talking about 11 kW drives, and asking in sci.electronics.basics?

Get a real electrician before you kill yourself or burn your building down.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

On Tue, 30 Oct 2012 13:57:16 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 10/30/2012 01:55 PM, etpm@whidbey.com wrote:
I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You're talking about 11 kW drives, and asking in sci.electronics.basics?

Get a real electrician before you kill yourself or burn your building down.

Cheers

Phil Hobbs
Greetings Phil,

I wired my building and all the machines. It all passed inspection by
WA state Labor and Industries inspectors. Puget Sound Energy said it
was one of the best wiring jobs they had seen. The machine in question
is running now but needs lower voltage to avoid a too high DC voltage
in the VFD when the spindle decelerates. The power to my shop averages
245 volts which is about 5 volts higher than what the VFD wants. I
just don't remember how to calculate for a buck xmfr since I only used
one once years ago. But looking on line at the square D web site I see
that the xmfrs I have are perfect for the job and are recommended by
the Sqaure D buck xmfr calculator. I still need to determine if my
phase converter is open delta. I think it is but need to be sure. But
thanks for your concern.
Eric

 

[George Herold]

On Oct 30, 1:55 pm, e...@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You might try asking at rec.crafts.metalworking.
(If you can wade through all the political dross.)

George H.

 

[Phil Hobbs]

On 10/30/2012 02:22 PM, etpm@whidbey.com wrote:

On Tue, 30 Oct 2012 13:57:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 10/30/2012 01:55 PM, etpm@whidbey.com wrote:
I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You're talking about 11 kW drives, and asking in sci.electronics.basics?

Get a real electrician before you kill yourself or burn your building down.

Cheers

Phil Hobbs
Greetings Phil,
I wired my building and all the machines. It all passed inspection by
WA state Labor and Industries inspectors. Puget Sound Energy said it
was one of the best wiring jobs they had seen. The machine in question
is running now but needs lower voltage to avoid a too high DC voltage
in the VFD when the spindle decelerates. The power to my shop averages
245 volts which is about 5 volts higher than what the VFD wants. I
just don't remember how to calculate for a buck xmfr since I only used
one once years ago. But looking on line at the square D web site I see
that the xmfrs I have are perfect for the job and are recommended by
the Sqaure D buck xmfr calculator. I still need to determine if my
phase converter is open delta. I think it is but need to be sure. But
thanks for your concern.
Eric

I'm relieved to hear that--you're the exception to the rule, then. If
you look in the archives, you'll find a whole bunch of posters that seem
to have had a death wish.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Allison]

<etpm@whidbey.com>

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?

** A 1.5kVA tranny with 25V secondary can deliver 60 amps continuous - this
equates to over 14kVA in a 240 volt system.

You have three of them so the total VA available is 42kVA, so is far more
than needed.

Get the wiring right - for Christ's sake.



..... Phil

 

[Jamie]

etpm@whidbey.com wrote:

On Tue, 30 Oct 2012 13:57:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:


On 10/30/2012 01:55 PM, etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You're talking about 11 kW drives, and asking in sci.electronics.basics?

Get a real electrician before you kill yourself or burn your building down.

Cheers

Phil Hobbs

Greetings Phil,
I wired my building and all the machines. It all passed inspection by
WA state Labor and Industries inspectors. Puget Sound Energy said it
was one of the best wiring jobs they had seen. The machine in question
is running now but needs lower voltage to avoid a too high DC voltage
in the VFD when the spindle decelerates. The power to my shop averages
245 volts which is about 5 volts higher than what the VFD wants. I
just don't remember how to calculate for a buck xmfr since I only used
one once years ago. But looking on line at the square D web site I see
that the xmfrs I have are perfect for the job and are recommended by
the Sqaure D buck xmfr calculator. I still need to determine if my
phase converter is open delta. I think it is but need to be sure. But
thanks for your concern.
Eric

You don't need a step down, you need a dynamic braking resistor to be
attached to the drive or, you need to configure the drive's stop
parameter to ramp to a stop and not coast to a stop. BUt if you're
trying to stop it fast, you should do both the dynamic R and the ramp to
stop set up.

The VFD should have terminals for the DB r and you must also turn
on the function in the drive. Select the proper DB-R that fits your
drive for maximum braking. Also, if the drive has vector mode in it, set
it up for open loop vector, that'll keep things tight..

Jamie

 

On Tue, 30 Oct 2012 18:39:50 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

etpm@whidbey.com wrote:
On Tue, 30 Oct 2012 13:57:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:


On 10/30/2012 01:55 PM, etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

You're talking about 11 kW drives, and asking in sci.electronics.basics?

Get a real electrician before you kill yourself or burn your building down.

Cheers

Phil Hobbs

Greetings Phil,
I wired my building and all the machines. It all passed inspection by
WA state Labor and Industries inspectors. Puget Sound Energy said it
was one of the best wiring jobs they had seen. The machine in question
is running now but needs lower voltage to avoid a too high DC voltage
in the VFD when the spindle decelerates. The power to my shop averages
245 volts which is about 5 volts higher than what the VFD wants. I
just don't remember how to calculate for a buck xmfr since I only used
one once years ago. But looking on line at the square D web site I see
that the xmfrs I have are perfect for the job and are recommended by
the Sqaure D buck xmfr calculator. I still need to determine if my
phase converter is open delta. I think it is but need to be sure. But
thanks for your concern.
Eric

You don't need a step down, you need a dynamic braking resistor to be
attached to the drive or, you need to configure the drive's stop
parameter to ramp to a stop and not coast to a stop. BUt if you're
trying to stop it fast, you should do both the dynamic R and the ramp to
stop set up.

The VFD should have terminals for the DB r and you must also turn
on the function in the drive. Select the proper DB-R that fits your
drive for maximum braking. Also, if the drive has vector mode in it, set
it up for open loop vector, that'll keep things tight..

Jamie
Greetings Jamie,

My first thought was braking resistors. Looking at the drive I could
see no braking resistors or even the option for braking resistors.
Reading the manual(always a good idea) for the Fuji Frenic 5000V2
drive reveals the reason: the drive uses regenerative braking. Braking
resistors aren't even an option and I wish they were. I don't know
more than the really basic about how VFDs work but the manual states
that if the AC supply voltage is too high then upon deceleration the
DC bus voltage can rise too high and cause the drive to turn off and
set an alarm. The machine was previously connected, at the last shop
it was in, to a Phase Perfect solid state phase converter (it is now
connected to a rotary phase converter,AKA RPC). Overvoltage alarm and
drive shutdown would also occur at the other shop but less often and
at random times. It doesn't always occur in my shop with deceleration
either. This random overvoltage problem is because the power at my
shop and at the machine's previous location 6 miles from my shop
averages 245 volts with spikes to 250 volts and above. This is a
little higher than spec for the drive. The voltage from my RPC is well
balanced and all the other CNC machines connected to it have no
problems. These include three lathes with Fanuc controls, which are
notoriously sensitive to unbalanced 3 phase, two machines with DC
spindle drives, a mill with Centroid control, and a Fada milll. The
Fadal mill came from the factory wired for and with the protection
circuitry for 480 volts so I have a transformer connected between the
RPC and the Fadal. And now it looks like buck wired xmfrs might be the
solution for the Fuji drive. I hope so because I'm gonna try it.
Eric

 

[Cydrome Leader]

etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.

 

On Wed, 31 Oct 2012 18:17:43 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

etpm@whidbey.com wrote:
I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.

Thanks for the reply. After getting all the info on the xmfrs I was

able to find them on the Square D website along with the tables for
choosing the correct xmfr. The ones in question are the proper ones to
use. Now I only need to determine whether my phase converter is open
delta or wye output.
Eric

 

On Wed, 31 Oct 2012 18:17:22 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

etpm@whidbey.com wrote:

On Wed, 31 Oct 2012 18:17:43 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:


etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.


Thanks for the reply. After getting all the info on the xmfrs I was
able to find them on the Square D website along with the tables for
choosing the correct xmfr. The ones in question are the proper ones to
use. Now I only need to determine whether my phase converter is open
delta or wye output.
Eric

Does that inverter allow you to operate single phase in? Many do and it
is a simply way to make the DC bus a little on the weaker side. You'll
get a reduction HP but you should still have enough.

Check the manual and see if you can run one leg missing coming in.

Jamie
It will not run on single phase. In fact, it will set an alarm if any

of the phases drops out. As far as loss of power goes, I already have
several parts that run the spindle load meter to 120% for brief
periods. 11 KW! It's cool to listen to the chips hitting the lathe
enclosure. They sound like hail.
Eric

 

[Jamie]

etpm@whidbey.com wrote:

On Wed, 31 Oct 2012 18:17:43 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:


etpm@whidbey.com wrote:

I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.


Thanks for the reply. After getting all the info on the xmfrs I was
able to find them on the Square D website along with the tables for
choosing the correct xmfr. The ones in question are the proper ones to
use. Now I only need to determine whether my phase converter is open
delta or wye output.
Eric

Does that inverter allow you to operate single phase in? Many do and it
is a simply way to make the DC bus a little on the weaker side. You'll
get a reduction HP but you should still have enough.

Check the manual and see if you can run one leg missing coming in.

Jamie

 

[Jamie]

etpm@whidbey.com wrote:

On Wed, 31 Oct 2012 18:17:22 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


etpm@whidbey.com wrote:


On Wed, 31 Oct 2012 18:17:43 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:



etpm@whidbey.com wrote:


I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.


Thanks for the reply. After getting all the info on the xmfrs I was
able to find them on the Square D website along with the tables for
choosing the correct xmfr. The ones in question are the proper ones to
use. Now I only need to determine whether my phase converter is open
delta or wye output.
Eric

Does that inverter allow you to operate single phase in? Many do and it
is a simply way to make the DC bus a little on the weaker side. You'll
get a reduction HP but you should still have enough.

Check the manual and see if you can run one leg missing coming in.

Jamie

It will not run on single phase. In fact, it will set an alarm if any
of the phases drops out. As far as loss of power goes, I already have
several parts that run the spindle load meter to 120% for brief
periods. 11 KW! It's cool to listen to the chips hitting the lathe
enclosure. They sound like hail.
Eric

And you verified that in the manual? Most of them you need to set a
parameter to allow it to operate on single phase.. I can only assume
you have looked at the manual for this and there is no option to set it
up that way..

One of the drives we do this to uses a "Ignore Phase Loss" and it
states that L3 is the phase you can drop out, internal control supply
uses L1 and L2.

Jamie

 

On Wed, 31 Oct 2012 19:54:15 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

etpm@whidbey.com wrote:

On Wed, 31 Oct 2012 18:17:22 -0500, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


etpm@whidbey.com wrote:


On Wed, 31 Oct 2012 18:17:43 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:



etpm@whidbey.com wrote:


I need to reduce the voltage to a CNC lathe. The spindle drive is the
only part of the machine that needs the lower voltage so I want to put
buck xmfrs between the spindle drive and the rotary phase converter
that I get me 3 phase power from. The spindle drive is a VFD and the
output is 11KW. I have access to three xmfrs that can be wired for the
voltage drop I need. I have the wiring charts. They are rated 1.5 KVA.
But that's when used as isolation xmfrs. Will these in the buck
configuration considering my 11 KW load and a 25 volt drop?
Thanks,
Eric

that's going to depend on the transformers. transformers in buck or boost
mode need only be rated for the voltage difference times the current they
handle.

not knowing what voltage you're trying to drop by 25 volts makes this
question unanswerable.

if you can defined the line voltage you have, what you want it to be and
the actual KVA required BY the VFD (not the load) , you can then figure
out what you need.


Thanks for the reply. After getting all the info on the xmfrs I was
able to find them on the Square D website along with the tables for
choosing the correct xmfr. The ones in question are the proper ones to
use. Now I only need to determine whether my phase converter is open
delta or wye output.
Eric

Does that inverter allow you to operate single phase in? Many do and it
is a simply way to make the DC bus a little on the weaker side. You'll
get a reduction HP but you should still have enough.

Check the manual and see if you can run one leg missing coming in.

Jamie

It will not run on single phase. In fact, it will set an alarm if any
of the phases drops out. As far as loss of power goes, I already have
several parts that run the spindle load meter to 120% for brief
periods. 11 KW! It's cool to listen to the chips hitting the lathe
enclosure. They sound like hail.
Eric

And you verified that in the manual? Most of them you need to set a
parameter to allow it to operate on single phase.. I can only assume
you have looked at the manual for this and there is no option to set it
up that way..

One of the drives we do this to uses a "Ignore Phase Loss" and it
states that L3 is the phase you can drop out, internal control supply
uses L1 and L2.

Jamie
Yes Jamie, I looked in the manual. This option was suggested in rcm.

Apparently this drive is unusual in a machine of this size. From what
other folks have said it is unusual for an 11KW VFD to use
regenerative braking. I've been told that this type of braking is
usually only used on much larger VFDs. Maybe that's why no single
phase option. Or maybe it's because the drive is 27 years old.
Eric